Since the ordered olivine lithium iron phosphate (LiFePO4) was discovered by Goodenough et al [1], it has been extensively and intensively studied as a cathode material for lithium ion battery due to its advantages include a high theoretical specific capacity (170 mAh/g), long cycle ability, high safety , low toxicity and potential for low cost [1,2], and much efforts have been made to understand and improve the performance of LiFePO4 in the past decade. Recently, Olivine LiFePO4 has been considered as the most promising cathode candidate for the next generation large-scale lithium ion battery used for hybrid electric vehicles (HEVs), electric vehicles (EVs) and large-scale energy storage systems for the sustainable energy needed for a low carbon society, such as the wind and solar power [3].
It is well-known in the lithium ion battery community that the slow diffusion of lithium ion and/or the low electronic conductivity in LiFePO4 limits its application as the power supply [2,5]. This apparent drawback had been compensated greatly in recent years through various materials synthesis and/or processing approaches, including the use of carbon coatings [6,7], particle size minimization [2, 8-13] and multivalent metal ions doping [14-16] and so on.
Recently, synthesized methods of LiFePO4 which take full considerations of carbon coating, particle size minimization and/or metal ions doping are gained more and more attention for improving the performances of cathode materials in terms of energy density, power density (rate capability), cycle life (stability). Nanosize carbon coated LiFePO4 cathode materials display very excellent electrochemistry properties. Kang and Ceder [17] obtained LiFePO4/C material with the size of about 50 nm by solid-state reaction and it showed good high-rate discharge performances, about 140 mAh/g at 20 C rate . Various methods have also been reported to prepare nanosize LiFePO4 particles with micron/nanostructures, which are highly desired for designing high-performance lithium-ion batteries with high volumetric energy density and good rate capability [18-21]. These structured LiFePO4/C particles create 3D electronic and ionic pathways, which facilitate electron migration in the solid phase and lithium ion diffusion in the liquid phase and provide the material excellent cyclability and superior rate capability. These micron/submicron-sized LiFePO4 well-structured particles have a high tap density and, as electrodes, show excellent rate capability and cycle stability.
There is an urgent need for novel technologies that find cost-effective synthesis methods to produce micron/submicron-sized nanostructured LiFePO4 particles , which have a high capacity and, as electrodes, show excellent high rate capability, retention and cycle stability.